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Dear Doctor: When to Spay

Q After leaving a dinner party late one night, my wife and I were walking to the train to head back to our apartment when a feral cat adopted us by meowing as loudly as she could and rubbing up against us. It turned out she was pregnant, which was fine with both of us, but she had an extremely difficult labor.

The single kitten she had been carrying died during birth; the poor mother kept trying to lick her baby alive. We decided to keep the cat and have her spayed — but after only about 10 days, she is back in heat, and now we have to wait. She is meowing rather obnoxiously and slithering along the floor toward me every chance she gets, even waking us up at night. How could she go into heat so quickly after giving birth?

Brian Longfellow

A Dear Brian: Reproductively, cats are different from dogs, people, horses, cows and most other mammalian species. Most female mammals have regular cycles that are about a month long (except dogs, whose cycles last about six months). The cycle starts with a period of time called pro-estrus, which consists of the hormonal changes leading up to ovulation. Then comes ovulation itself — the releasing of an egg from one of the ovaries. If the animal mates, she becomes pregnant. If not, the hormone levels drop, the egg is no longer viable, and a period of time passes before pro-estrus starts up again.

Cats, on the other hand, don’t ovulate after pro-estrus unless they mate. They are what is known in medical circles as induced ovulators. A male cat’s penis actually has little “spines” on it that stimulate the ovulatory process. Because of that, the hormone levels of a cat who doesn’t become pregnant when she reaches pro-estrus don’t have to “settle down” as much as in other species; there’s no egg to get rid of. That’s why she can enter pro-estrus again so quickly. Thus, what happened to your cat is not at all unusual. An intact female can go into pro-estrus as quickly as every week to 10 days.

Of course, if your cat’s kitten had lived and she nursed it, the lactation would have staved off pro-estrus, just the way nursing inhibits most species’ ability to release a new egg and become pregnant. But because there was no kitten to nurse, your cat was ready to become pregnant again as if she had never given birth.

If your cat’s pro-estrus is driving you crazy, speak to your veterinarian about inducing ovulation with a Q-tip, which is what many breeders do if they don’t want a cat to have kittens at a particular time. Once the cat ovulates, she won’t cycle again for two months — the typical length of a cat pregnancy — and you can have her spayed during that time.